It’s hard to overstate the importance of having functioning, reliable smoke detectors in your home. From 2007 through 2011, almost a quarter of all home fire-related deaths in the US occurred in homes with nonworking smoke alarms. While any functioning smoke alarm will alert you to problems if you’re at home, a smart alarm can alert you anywhere your smartphone has an Internet connection. For our tests, a former firefighter installed every currently available smart smoke alarm in her own home, both hardwired versions and battery-powered models, to find the best one for keeping you informed about your house’s status, whether you’re home or away. After mounting them to ceilings and walls, blowing smoke at them, fiddling with their batteries and accompanying apps, and generally pushing their buttons, we found that the second-generation Nest Protect smoke and carbon monoxide alarm is the best smart smoke alarm.